Rock drill



Jan. 14, 1941. A. D. BENNETT 2,228,338

ROCK DRILL Filed Aug. 3, 1940 INVENTOR Arflzza'fl Bennett HIS ATTORNEY Patented Jan. 14, 1941 UNITED STATES PATENT FFICE ROCK DRILL corporation of New Jersey Application August 3,

Claims.

This invention relates to rock drills, and more particularly to rock drills of the fluid actuated reciprocatory piston type.

One object of the invention is to assure the 5 uninterrupted movement of a piston of the rock drill.

Another object is to enable the piston to free itself in the event that it becomes stalled, as when a working implement actuated by the piston becomes stuck in the work.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawing accompanying this specification and in which similar reference, numerals refer to similar parts,

Figure l is an elevation, partly in section, of a rock drill constructed in accordance with the practice of the invention and showing the reciprocatory piston in one of the limiting positions, and

Figure 2 is a view similar to Figure 1 showing the piston in an intermediate position.

Referring more particularly to the drawing, 28

designates a rock drill comprising a cylinder 2| 25 having a piston chamber 22 to accommodate a reciprocatory hammer piston 23.

A closure 24 seals the rearward end of the piston chamber 22 and at the front end of the cylinder is a front head 25 containing a bushing 25 to guide an extension 21 of the piston 23.

The piston 23 is of the differential type having a reduced pressure surface 28 at its front end and a relatively large rear pressure surface 29, and pressure fluid is constantly supplied to the piston chamber forwardly of the piston to act against the pressure surface 28 through an inlet port 38 which opens into a supply conduit 3| attached to the side of the cylinder 2| as by a bolt or bolts 32.

The port 30 is preferably located a slight distance rearwardly of the front end of the piston chamber 22 and a port 33 of smaller flow area than the port 38 leads from the port 30 to the extreme front end of the piston chamber to assure a supply of pressure fluid beneath the piston 23 in the event that the piston assumes a position in which it blanks off the port 30.

The rear surface 29 of the piston is subjected intermittently to pressure fluid for actuating the piston on its working stroke.- The distribution of such pressure fluid is effected by valve mechanism designated, in its entirety, by 34 arranged adjacent the rear end of the piston chamher and comprising a valve chest 35 having a 1940, Serial No. 350,212

bushing 36 inserted in its rearward end to define a valve chamber 31 which communicates with the rear end of the piston chamber 22 through an inlet passage 38.

A flange 39 on the bushing 38 seats against 5 the rear end of the valve chest 35 and serves as a seat for a flange 48 of a plug 4| inserted into the rear end of the bushing to form a closure ;for the valve chamber 31. In the front ends of the bushing 35 and the valve chest 35 is a pas- 10 sage 42 that opens into the conduit 3|. The conduit abuts the front end of the valve chest 35 and issecured thereto by a bolt or bolts 43, and intermediate the ends of the valve chest is a pressure-fluid supply conduit 44 that communi- 15 cates with the valve chamber 31 through a passage 45 in the valve chest 35 and the bushing 36.

Withinthe valve chamber 31 is a reciprocable valve, 46 for controlling the admission of pressure fluid from the supply conduit 44 to the inlet .passage 38. The valve has a bore 41 extending entirely therethrough to pass pressure fluid to both ends of the valve chamber 31, andin the wall of the valve are a plurality of ports 48 that are in constant communication with the passage 45 so that pressure fluid may constantly flow'from supply through the valve chamber and the valve and associated channels to the front end of the piston chamber.

The front end of the valve constitutes an actuating surface 49 against which pressure fluid acts constantly tending to move the valve rearwardly and such pressure fluid is augmented by pressure fluid valved from the piston chamber 22 to an actuating surface 5|] onthe front end of a flange 5| of the valve located between the actuating surface 49 and the ports 48. The pressure fluid valved to the actuating surface 58 is conveyed thereto by a kicker passage 52 opening into the piston chamber 22 rearwardly of the inlet passage 38. A needle valve 53 threaded into the cylinder 2| extends into the front end of the kicker passage 52 to control the rate of flow of fluid into said passage, and'a port l8 leads from 45 an intermediate point in the kicker passage 52' tothe piston chamber 22 for exhausting the fluid from the actuating surface 58.

Therearward end of the valve 46 also serves as an actuating surface 54 and is constantly exposed to pressure fluid tendingto throw the valve forwardly. This actuating surface is of larger area than thewactuating surface 49 so that when the actuating surface 50 of the flange 5| is exposedtoatmospheric pressure the pressure fluid 5 5 acting against the actuating surface 54 will predominate over that acting against the surface 49 and move the valve 46 to its foremost limiting position.

A second flange 55 is arranged on the exterior of the valve 46 rearwardly of the ports 48 and cooperates with an internal flange 56 in the bushing 36 to control communication between the supply conduit 44 and the inlet passage 38.

In the form of rock drill illustrated, pressure fluid is exhausted to the atmosphere from only the rearward end of the piston chamber 122. The cylinder 2| is accordingly provided with a free exhaust port 51 that is controlled by the piston and so located that it will be uncovered when the piston approaches the foremost limiting position of its stroke. This is the mode of operation under conditions when the piston is free to complete its nominal stroke. There are instances, however, when the piston becomes stalled, as when the working implement it actuates and carries becomes stuck in the work, say, during the working stroke. In such event the piston may assume a position in which it overlies the exhaust port 51 and even though the rear end of the piston is subjected to pressure fluid it is often impossible for the piston to continue forwardly until the working implement is freed in the drill hole.

This latter procedure often involves the loss of much time and frequently results in damaging or breaking the working implement by the devices commonly employed for this purpose. In order to obviate this objectionable occurrence it is contemplated herein to free the working implement from the work through the force of the pressure fluid acting against the front end of the piston and to enable this force to become fully effective by first evacuating the rear end of the piston chamber through channels and by the operation of means other than those normally effecting the exhaust of fluid from the piston chamber. In furtherance of this end the valve chest 35 is provided with an atmospheric port 58 that serves, in eflect, as an auxiliary exhaust port for the rear end of the piston chamber. The exhaust port 58 is located rearwardly of the point of communication of the passage 38 with the valve chamber 31 and is controlled by a. valve 59 encircling the valve 46. The valve 59 has an internal flange 60 that slides on the periphery of the valve 46 and an external flange 6| on the periphery of the valve 46 engages the inner surface of the valve 59 to assist in guiding the latter valve.

The rearward end of the enlarged portion of the valve chamber 31 containing the valve 59 serves as a pressure chamber 62 into which pressure fluid is constantly conveyed from themterior of the valve 46 by a groove or grooves 63 extending across the actuating surface 54 and forwardly along the periphery of the valve 46. The grooves 63 are of such length that they will be in communication with the pressure chamber 62 in all positions of the valve 46. The pressure fluid thus admitted into the pressure chamber 62 acts against the rear end of the valve 59 which constitutes a pressure area 64. The valve 59 also has an actuating area 65, on its front end, of smaller area than the pressure area 64 and is subjected to pressure fluid whenever the valve 46 oocupies a position to admit pressure fluid into the rear end of the piston chamber 22.

The exhaust of pressure fluid from the pressure chamber 62 is effected through a passage 66 opening into the piston chamber 22 rearwardly of the point of communication of the kicker passage 52 with the piston chamber, and in the wall of the cylinder 2| is an atmospheric port 61 that lies directly opposite the port 19 and the outlet opening 68 of the passage 66. Communication between the port 61 and the outlet opening 68 is effected through an annular groove 69 in the periphery of the piston 23, and a needle valve 10 extending into the passage 66 is threaded into the wall of the cylinder 2| to control the rate of exhaust of fluid from the passage 66.

During the normal operation of the rock drill and with the hammer piston 23 and the valve 46 in the rearward positions illustrated in Figure 1, pressure fluid flows from the valve chamber 31 through the passage 38 into the rear end of the piston chamber and drives the piston 23 forwardly on its working stroke. During this stroke the annular groove 69 in the piston establishes communication between the port l9 of the kicker passage and the port 61 and the pressure fluid acting against the actuating surface 56 will be exhausted to the atmosphere. The valve 46 will then be shifted forwardly by the pressure fluid acting against the actuating surface 54 to cutoif the further admission of pressure fluid into the piston chamber. Thereafter the pressure fluid rearwardly of the piston will act expansively until the piston uncovers the exhaust port 51 to evacuate the rear end of the piston chamber.

This will take place immediately prior to the delivery of the blow against the work.

The pressure fluid acting against the constant pressure surface 28 in the front end of the piston will then return the piston to its initial position. During this movement the piston will again uncover the kicker passage 52 to admit pressure fluid to the actuating surface 50 for shifting the valve 46 rearwardly, thereby placing the inlet passage 38 in communication with pressure fluid 40 supply to charge the rear end of the piston chamber. v r

At the same time, pressure fluid will be present in the pressure chamber 62 for holding the valve 59 forwardly to prevent the passage of fluid; from the valve chamber, through the auxiliary exhaust port 58 to the atmosphere, and when the piston 23 reaches theposition in which the annular groove 69 communicates the outlet opening 68 of the passage 66 with the port 61, pressurer50 fluid may flow from the pressure chamber 62 to the atmosphere. The amount of pressure fluid thus exhausted to the atmosphere is slight, however, since the needle valve 10 will be adjusted in such wise as to assure a holding pressure 0n.1;he; -5 5 pressure area 64 during the slight interval of time required for the passage of the annular groove across theoutlet opening 68 and the valve 59 will remain stationary in its foremost limiting position. In the event that the piston 23 becomes stalled in a position in which it still covers the exhaust port 51, as illustrated in Figure 2, so thatthe annular groove 69 will communicate the outlet opening 68 of the passage 66 with the port 61 455 rearwardly and withdraw the working implement from the binding material.

I claim:

1. A pressure fluid actuated rock drill, comprising a cylinder having a piston chamber, a piston in the piston chamber, an exhaust port for the piston chamber controlled by the piston, a valve chest having a valve chamber, a valve in the valve chamber to valve pressure fluid into the piston chamber, an auxiliary exhaust port for the piston chamber, and a valve for controlling the auxiliary exhaust port and being controlled by the piston.

2. A pressure fluid actuated rock drill, comprising a cylinder having a piston chamber, a piston in the piston chamber, an exhaust port for the piston chamber controlled by the piston, a valve chest having a valve chamber, a valve in the valve chamber to valve pressure fluid into the piston chamber, an auxiliary exhaust port for the piston chamber, and a valve for controlling the auxiliary exhaust port having a pressure area normally subjected to pressure fluid for holding it in position to prevent the exhaust of fluid through the auxiliary exhaust port.

3. A pressure fluid actuated rock drill, comprising a cylinder having a piston chamber, a piston in th piston chamber, an exhaust port for the piston chamber controlled by the piston, means for valving pressure fluid into the piston chamber to actuate the piston, an auxiliary exhaust port for an end of the piston chamber, a valve for controlling the auxiliary exhaust port having a pressure area normally subfected to pressure fluid for holding the valve in position to prevent the exhaust of fluid through the auxiliary exhaust port, an actuating surface on the valve opposed to the pressure surface and being subjected to pressure fluid for shifting the valve to open the auxiliary exhaust port, an exhaust passage controlled by the piston for exhausting the pressure fluid acting against the pressure area, and means for controlling the rate of flow of fluid from the exhaust passage.

4. A pressure fluid actuated rock drill, comprising a cylinder having a piston chamber, a piston in the piston chamber, an exhaust port for the piston chamber controlled by the piston, means for valving pressure fluid into the piston chamber to actuate the piston, an auxiliary exhaust port for an end of the piston chamber, a valve for controlling the auxiliary exhaust port having a pressure area, means defining a passage for constantly conveying pressure fluid to the pressure area for holding the valve in position to prevent the exhaust of fluid through the auxiliary exhaust port, an actuating surface on the valve opposed to and of smaller area than the pressure area subjected to pressure fluid for shifting the valve to open the auxiliary exhaust port, and means for controlling the rate of exhaust of fluid from the pressure area.

5. A pressure fluid actuated rock drill, comprising a cylinder having a piston chamber, a piston in the piston chamber having a front pressure surface constantly subjected to pressure fluid and a rear pressure surface, a main exhaust port in the piston chamber controlled by the piston, means for valving pressure fluid intermittently to the rear pressure surface, means for effecting the cut-off of pressure fluid to the rear pressure surface prior to the uncovering of the exhaust port by the piston, an auxiliary exhaust port for the rear end of the piston chamber, a valve for controlling the auxiliary exhaust port having a pressure area, means defining a passage for constantly conveying pressure fluid to the pressure area of the valve for holding the valve in position to prevent the exhaust of fluid through the auxiliary exhaust port, an actuating surface on the valve opposed to and of smaller area than the pressure area of the valve subjected to pressure fluid for shifting the valve to open the auxiliary exhaust port for communicating the rear pressure surface with the atmosphere whenever the piston becomes stalled in a position in which it overlies the main exhaust port, and means for controlling the rate of exhaust of fluid from the pressure area of the valve.

ARTHUR D. BENNETT. 

